COMPARATIVE TOXICITY OF PARAQUAT AND 2,4-DICHLOROPHENOXYACETIC ACID HERBICIDES ON THE SURVIVAL OF THE AFRICAN MOUND BUILDING TERMITE (MACROTERMES BELLICOSUS)

ABSTRACT

Evaluation of herbicide pollution in a terrestrial ecosystem is of great concern to entomologists and environmentalists due to the effects of these herbicides on the ecosystem; especially on non-tagged target species. Paraquat (PQ) and 2,4-Dichlorophenoxyacetic acid (2,4-D) herbicides are effective herbicides used to control weed in many countries including Nigeria. This study therefore investigates the effects of paraquat and 2,4-D on the survival of the worker caste of the African mound-building termites (Macrotermes bellicosus). The termites were exposed to different concentrations above and below the recommend concentration of the herbicides; which wereas 7.5ml and 6.25ml per 500ml of water for paraquat and 2,4-D, respectively. Percentage mortality of worker termites was recorded after 6, 12, 18, 24 and 30-hour exposure, with mortality rate being high regardless of herbicides or concentrations used. Higher mortality of worker termites were recorded at higher concentrations, which increased over time. Percentage mortality caused by the recommended concentrations of 2,4-D was significantly higher than that of paraquat after 6 hours exposure. After 33-hour exposure, all concentrations tested caused 100% mortality in termites. Results from this showed that levels below the recommended concentrations of paraquat and 2,4-D caused severe mortality in termites suggesting study suggests that paraquat and 2,4-D herbicides are toxic to termites, and could inhibit their performances roles in an natural and semi-natural ecposystems. It is therefore recommended that alternative methods of weed control (biological methods) be employed by farmers, and governing authorities should put appropriate measures to ensure that farmers adhere.